In the production of elongated siding panels of extruded polyvinylchloride (vinyl) or similar plastics materials, it is highly desirable to provide for attaching the siding panels in an overlapping manner to the outer surface of the building so that each panel may expand and contract longitudinally with changes in environmental temperature. For example, it is possible for a 12' siding panel of extruded vinyl to change in length by as much as 5/8" due to thermal expansion and contraction. In some forms of extruded vinyl siding panels, for example, as disclosed in U.S. Pat. No. 3,520,099 and No. 4,102,106, the upper edge portion of each panel is provided with longitudinally extending and longitudinally spaced slots through which fasteners or nails are inserted for supporting the siding panel and for attaching the panel to the outer surface of a building. Preferably, the nails are not tightly driven so that the panel is free to shift or expand and contract longitudinally relative to the nails without causing the panel to buckle or distort. However, with such panels, it is difficult to use a power driven nailer and precisely control the force applied by each nail head against the upper edge portion of the siding panel.
It has also been known to support the upper edge portions of siding panels with longitudinally spaced clips which are positively nailed to the outer surface of the building, for example, as disclosed in U.S. Pat. No. 2,820,535 and No. 3,226,901. If properly constructed and installed, the clips may provide for longitudinal thermal expansion and contraction of each panel relative to the clips. However, such clips are manually attached to the upper edge portion of each siding panel prior to or during installation of the panel and thus require additional labor and time for installing overlapping siding panels on the outer surface of the building.
Overlapping vinyl siding panels have also been installed on the outer surface of a building with the use of longitudinally extending support strips of extruded plastics material or roll-formed metal, for example, as disclosed in U.S. Pat. No. 3,214,876, No. 3,417,531, No. 3,552,078, No. 4,096,679 and No. 4,669,238. The separate support strips are usually attached to the siding panels after production of the panels or immediately prior to installing the panels onto the outer surface of a building. These longitudinally extending support strips add significantly to the cost of the siding panel and also require additional labor and time for installing the overlapping siding panels. In addition, if the support strips are free to slide longitudinally relative to their corresponding siding panels, each panel must be carefully handled during transport and installation.
In above-mentioned U.S. Pat. No. 4,669,238, in which the applicant herein is a co-inventor, a roll-formed or extruded metal support strip is provided with a deformation or dimple at each end of the support strip. The dimples cooperate with notches within the corresponding end portions of the siding panel to limit longitudinal movement of each support strip relative to its supporting siding panel during handling and installing the siding panels. When it is necessary to cut a siding panel to a shorter length, the siding panel should be renotched, and the support strip redimpled and cut at a slightly shorter length to provide for overlapping end portions of longitudinally adjacent panels.